Primary pulmonary hyalinizing clear cell carcinoma with vocal-cord squamous cell carcinoma: a case report with systematic review

BACKGROUND: Primary pulmonary hyalinizing clear cell carcinoma (HCCC) is a low-grade salivary gland-type carcinoma. Until now, 23 cases of pulmonary HCCC have been reported. CASE PRESENTATION: Here, we present a patient with primary pulmonary HCCC along with vocal-cord squamous cell carcinoma (SCC) revealed by biopsy examination. The patient underwent radiotherapy for vocal-cord SCC, followed by right upper lobectomy and lymph node dissection 10 months later. Histology revealed polygonal cells with eosinophilic or clear cytoplasm in the myxoid matrix together with hyaline degeneration. The tumor involved the whole layer of the segmental bronchus and regionally involved the alveolar tissue along with one intrapulmonary lymph node. Targeted RNA sequencing revealed Ewing Sarcoma Breakpoint Region 1 (EWSR1)- activating transcription factor 1 (ATF1) fusion. We analyzed the data on pulmonary malignant tumors between 2000 and 2019 in the Surveillance, Epidemiology, and End Results (SEER) database and reviewed all cases of pulmonary HCCC with EWSR1 fusion by searching PubMed. The results showed that head and neck (HN) adenoid cystic carcinoma (ACC) (47.89%) and HNSCC (22.54%) were the most common carcinomas occurring with pulmonary salivary gland-type malignant tumors. Screening of 24 cases of pulmonary HCCC with EWSR1 fusion revealed that five cases demonstrated lymph node metastases and only two had documented tumor recurrences. HCCC is rare and easily misdiagnosed as SCC, but the treatment regimen differs between pulmonary HCCC and SCC. CONCLUSIONS: Hence, pulmonary tumors with clear cells must be diagnosed with caution. Next-generation sequencing (NGS) may be useful for diagnosis, especially in cases with a history of squamous cell carcinoma (SCC).